Group selection was used as a popular explanation for adaptations, especially by British zoologist Vero C. Wynne-Edwards in the 1960s. He provided a framework for understanding the balance between altruistic and self-interested adaptations, proposing that group-level adaptations for group-level survival were possible. Supported more recently by others including David Sloan Wilson, an evolutionary biologist and author at the State University of New York at Binghamton

1. T Y B Sc. Zoology Notes: Paper IV –Animal Behavior
A model that examines the behaviour of parasites infecting their hosts renders the evolutionary
paradigm of group selection unnecessary, say scientists in Canada and the United Kingdom 1.
Why organisms display behaviours or other adaptations that aren't directly beneficial to them is a
question that has intrigued biologists and caused conflict between different schools of thought for
generations. Bees that spend their lives serving their queen, for example, and elephants that care
for the offspring of others in the herd are participating in cooperative acts that may undermine
their own chances of reproducing.
Group selection was used as a popular explanation for adaptations, especially by British zoologist
Vero C. Wynne-Edwards in the 1960s. He provided a framework for understanding the balance
between altruistic and self-interested adaptations, proposing that group-level adaptations for
group-level survival were possible. Voiced more recently by others including David Sloan Wilson,
an evolutionary biologist and author at the State University of New York at Binghamton, group
theory has come to mean selection and adaptation at multiple levels: traits can confer benefits to
the individual, the family, the group or the society.
(a) Group selection is a means by which cooperative behavior might evolve, though
chances are that in the real world it makes little contribution except, perhaps, in the
evolution of culturally learned behavior that is cooperative
(b) The basic idea is that two groups are competing either over resources or directly
fighting against each other; if in one group individuals cooperate whereas in the
other they do not, then the overall fitness of the cooperating group will exceed that
of the non-cooperating group, thus driving the latter, along with its non-cooperative
behavior, to extinction
(c) For example, humans even within large groups are very willing to put aside
differences to fight against a common enemy.
Williams presents a simple of model of biotic adaptation, and a more complicated model by
Wright which makes use of "drift". First, biotic adaptation is theoretically possible, as the following
figure shows.
By Prof. S D Rathod
Dept. of Zoology
B N Bandodkar College of Science, Thane, India

2. T Y B Sc. Zoology Notes: Paper IV –Animal Behavior
Sewall Wright is known for the notion of "drift". If a group is small and relatively isolated, a
peculiar gene may become dominant within the group by genetic drift. The holder of such a gene
may be disadvantageous for the holder but advantageous to the group (e.g., by altruistic
behavior), and the group may become larger (the group is successful vis-a-vis other groups). And if
the group becomes large enough, some of the holders of this gene may move into other groups,
and a similar process can begin within these new groups.
A. Animals sometimes restrain their reproduction:
Animals restraining from reproduction and allowing the counterparts to reproduce, is the
indication of the group selection. Because doing this an individual looses its own genetic
relationship but help the other individuals with different genotypes to enhance the group and
their co-evolution. But doing this even though the individual is at lost it benefits group as a hole to
carry their generations in future successfully. Spatial populations of predators and prey have also
By Prof. S D Rathod
Dept. of Zoology
B N Bandodkar College of Science, Thane, India

3. T Y B Sc. Zoology Notes: Paper IV –Animal Behavior
been shown to show restraint of reproduction at equilibrium, both individually and through social
communication
B. The haystack model and trait groups
Maynard Smith can be credited with what has become known as the "haystack model" of group
selection. As a non-mathematical introduction to the idea, imagine a group of animals that spend
most of their time living and breeding in haystacks but that occasionally all come out of their
haystacks simultaneously, mix together and then separate into equal groups, which once again go
off to inhabit separate haystacks.
Each of these two traits works on a different level of selection. Within the individual haystacks the
selfish organisms benefit in terms of evolutionary fitness. This is because the selfish organisms
benefit from the actions of the altruistic organisms but do not pay any of the evolutionary costs
for being altruistic (sacrificing some good for that of others). Thus, in each generation the number
of altruists in the group would shrink compared to the number of selfish organisms. As a result
one might first think that a group beneficial trait, especially an altruistic one, would be doomed to
eventually die out. But we must remember the strange nature of these hypothetical organisms.
Every so often, at the same time, all the members of all the haystacks form one large group,
randomly assort into equal groups, and then move back into the haystacks. Because of this an
altruistic behavior can take hold by the following reasoning. While the number of selfish
organisms in each haystack increases in percentage every generation, the total population of
haystacks that contain altruists produce more offspring over all than those that do not. This means
that populations with altruists are going to be over-represented when all the haystacks are
abandoned to form a larger group. So long as the number of generations spent in each haystack is
not so long as to dramatically reduce the number of altruists, and so long as the group benefit of
the altruistic trait is significant enough, the number of altruists in all the haystack populations can
rise.
C. Multilevel selection theory
David Sloan Wilson, the developer of Multilevel Selection Theory (MLS) compares the many layers
of competition and evolution to the "Russian Matryoska Dolls" within one another. The lowest
level is the genes, next come the cells, and then the organism level and finally the groups. The
different levels function cohesively to maximize fitness, or reproductive success. After establishing
these levels, MLS goes further by saying that selection for the group level, which is competition
between groups, must outweigh the individual level, which is individuals competing within a
group, for a group-beneficiating trait to spread. MLS theory focuses on the phenotype this way
because it looks at the levels that selection directly acts upon
Experimental results starting in the late 1970s demonstrated that group selection was far more
effective than the then-current theoretical models had predicted. A review of this experimental
work has shown that the early group selection models were flawed because they assumed that
genes acted independently, whereas in the experimental work it was apparent that gene
By Prof. S D Rathod
Dept. of Zoology
B N Bandodkar College of Science, Thane, India

4. T Y B Sc. Zoology Notes: Paper IV –Animal Behavior
interaction, and more importantly, genetically based interactions among individuals, were an
important source of the response to group selection (e.g.). As a result many are beginning to
recognize that group selection, or more appropriately multilevel selection, is potentially an
important force in evolution.
For humans, a highly pro-social, cognitive thinking species, social norms can be seen as a means of
reducing the individual level variation and competition and shift selection in humans to the group
level. Wilson ties the MLS theory regarding humans to another upcoming theory known as gene-
culture evolution by acknowledging that culture seems to characterize a group-level mechanism
for human groups to adapt to environmental changes. Methods of testing MLS include social
psychological experimentation and multilevel modeling equations.
D. Group selection due to differing ESSs
The problem with group selection is that for a whole group to get a single trait, it must spread
through the whole group first by regular evolution. But, as J. L. Mackie suggested, when there are
many different groups, each with a different Evolutionarily Stable Strategy (ESS), there is selection
between the different ESSs, since some are worse than others. For example, a group where
altruism arose would outcompete a group where every creature acted in its own interest (see, for
instance, the ESSs created by Koinophilia).
E. Some examples:
1. In cooperative breeding, not only the parents but related and sometimes unrelated
individuals of the same species help in looking after the nest, eggs and offspring, i.e.
appear to show altruistic behavior. Some studies have shown that environmental factors,
such as shortage of territories or unpredictability of resources, predispose birds to
cooperative breeding, although environment is only one of the factors involved. Numerous
studies deal with the genetic basis of cooperative breeding. Kinship (inclusive fitness) may
often give a satisfactory explanation, but is less satisfactory when non-related individuals
act as “helpers”, and there is increasing evidence that non-related helpers are indeed quite
common. Therefore, explanations based on group augmentation (increase in the density
and size of the population) are attempted, because it seems obvious that the size of a
group enhances its genetic diversity and thereby its evolutionary survivability.
2. In eusociality (formation of ‘superorganisms’, ‘states’), as found for example in bees, ants
and termites, the ‘altruistic’ behaviour is far more advanced than in cooperative breeding.
Most of the individuals of an insect ‘state’ have lost their ability to reproduce altogether
and devote their entire energy to supporting the colony. Until recently, the commonly
accepted explanation.
By Prof. S D Rathod
Dept. of Zoology
B N Bandodkar College of Science, Thane, India

5. T Y B Sc. Zoology Notes: Paper IV –Animal Behavior
3. Humans differ from other animals in possessing a huge and complex brain that has
permitted development of culture. Ethical convictions usually involving altruistic principles
are part of culture and transmitted by tradition. Although genes certainly provide the
general basis for culture formation in being responsible for development of the brain in the
first place, it is unlikely that they are solely (if at all) responsible for each cultural trait.
Dawkins, for example, claims that genes are not significant in the formation of human
cultural traits, some sociobiologists at least attribute a greater role to them. Is it possible
that only humans can truly act in an altruistic way, for example because they are able to
arrive at ethical philosophical principles as in Buddhism, Hinduism.
F. Critisism :Group selection isn’t widely accepted by evolutionists for several
reasons.
1. First, it’s not an efficient way to select for traits, like altruistic behavior, that are supposed
to be detrimental to the individual but good for the group. Groups divide to form other
groups much less often than organisms reproduce to form other organisms, so group
selection for altruism would be unlikely to override the tendency of each group to quickly
lose its altruists through natural selection favoring cheaters.
2. Further, we simply have little evidence that selection on groups has promoted the
evolution of any trait.
3. Finally, other, more plausible evolutionary forces, like direct selection on individuals for
reciprocal support, could have made us prosocial. These reasons explain why only a few
biologists, like [David Sloan] Wilson and E. O. Wilson (no relation), advocate group
selection as the evolutionary source of cooperation. Group selection describes natural
selection operating between groups of organisms, rather than between individuals. This
would produce adaptations that benefit the group, rather than the individual. Darwin's
theory of evolution was based upon individual selection, and he rejected the idea of
group selection.
By Prof. S D Rathod
Dept. of Zoology
B N Bandodkar College of Science, Thane, India